Asymmetric dimethylarginine (ADMA) is an inhibitor of endothelial nitric oxide synthase (eNOS). eNOS is responsible for the normal production of endothelium-derived nitric oxide (EDNO) which is important for normal vasodilation and protection against atherosclerosis. ADMA is found to be elevated in persons with risk factors for atherosclerosis and with heart and renal failure. Serum ADMA correlates better than cholesterol with indicators of vascular function such as reduced EDNO activity, impaired vasodilation, increased white blood cell adhesion to blood vessels. ADMA is currently assayed by a cumbersome, time-consuming, and expensive procedure. A new method based on enzymatic immunassay technology by which blood ADMA could be measured rapidly, accurately and inexpensively will be desirable to researchers and clinicians. In this proposal, a prototype assay platform is used to refine an assay procedure. Following refinement, the assay is tested against the current method for determination of precision. The assay is then used to further determine the role ADMA plays in cardiovascular disease. In one clinical study, plasma ADMA concentration is compared to EDNO bioactivity measured by ultrasound techniques. A second cohort study compares ADMA concentration to cardiovascular death rate. PROPOSED COMMERCIAL APPLICATIONS: The commercial goal of Phase II will be to provide data demonstrating the sensitivity and precision of the assay and to demonstrate the importance of ADMA in cardiovascular disease.